Static Semantics Research Articles

Polymorphic symmetric multiple dispatch with variance

Many object-oriented languages provide method overloading, which allows multiple method declarations with the same name. For a given method invocation, in order to choose what method declaration to invoke, multiple dispatch considers the run-time types of the arguments. While multiple dispatch can support binary methods (such as mathematical operators) intuitively and consistently, it is difficult to guarantee that calls will be neither ambiguous nor undefined at run time, especially in the presence of expressive language features such as multiple inheritance and parametric polymorphism. Previous efforts have formalized languages that include such features by using overloading rules that guarantee a unique and type-sound resolution of each overloaded method call; in many cases, such rules resolve ambiguity by treating the arguments asymmetrically. Here we present the first formal specification of a strongly typed object-oriented language with symmetric multiple dispatch, multiple inheritance, and parametric polymorphism with variance. We define both a static (type- checking) semantics and a dynamic (dispatching) semantics and prove the type soundness of the language, thus demonstrating that our novel dynamic dispatch algorithm is consistent with the static semantics. Details of our dynamic dispatch algorithm address certain technical challenges that arise from structural asymmetries inherent in object-oriented languages (e.g., classes typically declare ancestors explicitly but not descendants).

Decision procedures for path feasibility of string-manipulating programs with complex operations

The design and implementation of decision procedures for checking path feasibility in string-manipulating programs is an important problem, with such applications as symbolic execution of programs with strings and automated detection of cross-site scripting (XSS) vulnerabilities in web applications. A (symbolic) path is given as a finite sequence of assignments and assertions (i.e. without loops), and checking its feasibility amounts to determining the existence of inputs that yield a successful execution. Modern programming languages (e.g. JavaScript, PHP, and Python) support many complex string operations, and strings are also often implicitly modified during a computation in some intricate fashion (e.g. by some autoescaping mechanisms). In this paper we provide two general semantic conditions which together ensure the decidability of path feasibility: (1) each assertion admits regular monadic decomposition (i.e. is an effectively recognisable relation), and (2) each assignment uses a (possibly nondeterministic) function whose inverse relation preserves regularity. We show that the semantic conditions are expressive since they are satisfied by a multitude of string operations including concatenation, one-way and two-way finite-state transducers, replaceall functions (where the replacement string could contain variables), string-reverse functions, regular-expression matching, and some (restricted) forms of letter-counting/length functions. The semantic conditions also strictly subsume existing decidable string theories (e.g. straight-line fragments, and acyclic logics), and most existing benchmarks (e.g. most of Kaluza’s, and all of SLOG’s, Stranger’s, and SLOTH’s benchmarks). Our semantic conditions also yield a conceptually simple decision procedure, as well as an extensible architecture of a string solver in that a user may easily incorporate his/her own string functions into the solver by simply providing code for the pre-image computation without worrying about other parts of the solver. Despite these, the semantic conditions are unfortunately too general to provide a fast and complete decision procedure. We provide strong theoretical evidence for this in the form of complexity results. To rectify this problem, we propose two solutions. Our main solution is to allow only partial string functions (i.e., prohibit nondeterminism) in condition (2). This restriction is satisfied in many cases in practice, and yields decision procedures that are effective in both theory and practice. Whenever nondeterministic functions are still needed (e.g. the string function split), our second solution is to provide a syntactic fragment that provides a support of nondeterministic functions, and operations like one-way transducers, replaceall (with constant replacement string), the string-reverse function, concatenation, and regular-expression matching. We show that this fragment can be reduced to an existing solver SLOTH that exploits fast model checking algorithms like IC3. We provide an efficient implementation of our decision procedure (assuming our first solution above, i.e., deterministic partial string functions) in a new string solver OSTRICH. Our implementation provides built-in support for concatenation, reverse, functional transducers (FFT), and replaceall and provides a framework for extensibility to support further string functions. We demonstrate the efficacy of our new solver against other competitive solvers.

Live functional programming with typed holes

Live programming environments aim to provide programmers (and sometimes audiences) with continuous feedback about a program's dynamic behavior as it is being edited. The problem is that programming languages typically assign dynamic meaning only to programs that are complete, i.e. syntactically well-formed and free of type errors. Consequently, live feedback presented to the programmer exhibits temporal or perceptive gaps. This paper confronts this "gap problem" from type-theoretic first principles by developing a dynamic semantics for incomplete functional programs, starting from the static semantics for incomplete functional programs developed in recent work on Hazelnut. We model incomplete functional programs as expressions with holes, with empty holes standing for missing expressions or types, and non-empty holes operating as membranes around static and dynamic type inconsistencies. Rather than aborting when evaluation encounters any of these holes as in some existing systems, evaluation proceeds around holes, tracking the closure around each hole instance as it flows through the remainder of the program. Editor services can use the information in these hole closures to help the programmer develop and confirm their mental model of the behavior of the complete portions of the program as they decide how to fill the remaining holes. Hole closures also enable a fill-and-resume operation that avoids the need to restart evaluation after edits that amount to hole filling. Formally, the semantics borrows machinery from both gradual type theory (which supplies the basis for handling unfilled type holes) and contextual modal type theory (which supplies a logical basis for hole closures), combining these and developing additional machinery necessary to continue evaluation past holes while maintaining type safety. We have mechanized the metatheory of the core calculus, called Hazelnut Live, using the Agda proof assistant. We have also implemented these ideas into the Hazel programming environment. The implementation inserts holes automatically, following the Hazelnut edit action calculus, to guarantee that every editor state has some (possibly incomplete) type. Taken together with this paper's type safety property, the result is a proof-of-concept live programming environment where rich dynamic feedback is truly available without gaps, i.e. for every reachable editor state.

Modifying the severity of Jargon aphasia using inter-stimulus manipulations

Modifying the severity of Jargon aphasia using inter-stimulus manipulations

I Do Not Exist. Problems for Dynamic Semantics

According to dynamic semantics, what is said by an utterance of a sentence is determined by how the common ground is affected by the acceptance of such utterance. It has been claimed that dynamic semantics offers an account of what is said by an utterance in a context that excels that of traditional static semantics. Assertions of negative existential constructions, of the form ‘X does not exist’, are a case in point. These assertions traditionally pose a problem for philosophers of language. A recent proposal, owed to Clapp (2008), argues that static semantics is unable to solve the problem and offers a dynamic semantics account that promises to succeed. In this paper I want to challenge this account and, more generally, the scope of the dynamic semantics framework. I will offer a counterexample, inspired by “answering machine” uses of indexical and demonstrative expressions, to show how dynamic semantics fails. I conclude by considering the merits of both static and dynamic accounts.

Age-related differences in the neural bases of phonological and semantic processes in the context of task-irrelevant information

As we age we have increasing difficulty with phonological aspects of language production. Yet semantic processes are largely stable across the life span. This suggests a fundamental difference in the cognitive and potentially neural architecture supporting these systems. Moreover, language processes such as these interact with other cognitive processes that also show age-related decline, such as executive function and inhibition. The present study examined phonological and semantic processes in the presence of task-irrelevant information to examine the influence of such material on language production. Older and younger adults made phonological and semantic decisions about pictures in the presence of either phonologically or semantically related words, which were unrelated to the task. FMRI activation during the semantic condition showed that all adults engaged typical left-hemisphere language regions, and that this activation was positively correlated with efficiency across all adults. In contrast, the phonological condition elicited activation in bilateral precuneus and cingulate, with no clear brain–behavior relationship. Similarly, older adults exhibited greater activation than younger adults in several regions that were unrelated to behavioral performance. Our results suggest that as we age, brain–behavior relations decline, and there is an increased reliance on both language-specific and domain-general brain regions that are seen most prominently during phonological processing. In contrast, the core semantic system continues to be engaged throughout the life span, even in the presence of task-irrelevant information.

Scopes as types

Scope graphs are a promising generic framework to model the binding structures of programming languages, bridging formalization and implementation, supporting the definition of type checkers and the automation of type safety proofs. However, previous work on scope graphs has been limited to simple, nominal type systems. In this paper, we show that viewing scopes as types enables us to model the internal structure of types in a range of non-simple type systems (including structural records and generic classes) using the generic representation of scopes. Further, we show that relations between such types can be expressed in terms of generalized scope graph queries. We extend scope graphs with scoped relations and queries. We introduce Statix, a new domain-specific meta-language for the specification of static semantics, based on scope graphs and constraints. We evaluate the scopes as types approach and the Statix design in case studies of the simply-typed lambda calculus with records, System F, and Featherweight Generic Java.

Enhanced semantic involvement during word recognition in children with dyslexia

We investigated whether children with dyslexia show enhanced semantic involvement as compensation for deficient phonological processing during reading. Phonological and semantic processing during reading and moderating effects of word frequency and word length in children with and without dyslexia were examined using a picture–word priming paradigm. Participants were 61 children with dyslexia and 50 typical readers in Grade 6 of primary school. Primes were either semantically or phonologically (shared onset and rime) related or unrelated to their target word. Results showed that priming effects were stronger in children with dyslexia than in typical readers in the semantic condition but did not differ between groups in the phonological condition. Overall, word length and word frequency effects were stronger for children with dyslexia than for typical readers, but word length and word frequency did not affect priming effects differently for the two groups. In both groups, only semantic priming effects were stronger for low-frequency longer words. Finally, individual word and pseudoword reading efficiency correlated with priming effects only in the semantic condition and only in children with dyslexia. It can be concluded that children with dyslexia, compared with typical readers, rely more on semantic information in word reading but do not show deficient phonological activation during reading compared with typical readers.

Phonemic and Semantic Verbal Fluency in Sex Chromosome Aneuploidy: Contrasting the Effects of Supernumerary X versus Y Chromosomes on Performance.

Past research suggests that youth with sex chromosome aneuploidies (SCAs) present with verbal fluency deficits. However, most studies have focused on sex chromosome trisomies. Far less is known about sex chromosome tetrasomies and pentasomies. Thus, the current research sought to characterize verbal fluency performance among youth with sex chromosome trisomies, tetrasomies, and pentasomies by contrasting how performance varies as a function of extra X number and X versus Y status. Participants included 79 youth with SCAs and 42 typically developing controls matched on age, maternal education, and racial/ethnic background. Participants completed the phonemic and semantic conditions of a verbal fluency task and an abbreviated intelligence test. Both supernumerary X and Y chromosomes were associated with verbal fluency deficits relative to controls. These impairments increased as a function of the number of extra X chromosomes, and the pattern of impairments on phonemic and semantic fluency differed for those with a supernumerary X versus Y chromosome. Whereas one supernumerary Y chromosome was associated with similar performance across fluency conditions, one supernumerary X chromosome was associated with relatively stronger semantic than phonemic fluency skills. Verbal fluency skills in youth with supernumerary X and Y chromosomes are impaired relative to controls. However, the degree of impairment varies across groups and task condition. Further research into the cognitive underpinnings of verbal fluency in youth with SCAs may provide insights into their verbal fluency deficits and help guide future treatments. (JINS, 2018, 24, 917-927).

Pointing to the right side? An ERP study on anaphora resolution in German Sign Language.

Sign languages use the horizontal plane to refer to discourse referents introduced at referential locations. However, the question remains whether the assignment of discourse referents follows a particular default pattern as recently proposed such that two new discourse referents are respectively assigned to the right (ipsilateral) and left (contralateral) side of (right handed) signers. The present event-related potential study on German Sign Language investigates the hypothesis that signers assign distinct and contrastive referential locations to discourse referents even in the absence of overt localization. By using a semantic mismatch-design, we constructed sentence sets where the second sentence was either consistent or inconsistent with the used pronoun. Semantic mismatch conditions evoked an N400, whereas a contralateral index sign engendered a Phonological Mismatch Negativity. The current study provides supporting evidence that signers are sensitive to the mismatch and make use of a default pattern to assign distinct and contrastive referential locations to discourse referents.

Merlin: a language server for OCaml (experience report)

We report on the experience of developing Merlin, a language server for the OCaml programming language in development since 2013. Merlin is a daemon that connects to your favourite text editor and provides services that require a fine-grained understanding of the programming language syntax and static semantics: instant feedback on warnings and errors, autocompletion, "type of the code under the cursor", "go to definition", etc. Language servers need to handle incomplete and partially-incorrect programs, and try to be incremental to minimize recomputation after small editing actions. Merlin was built by carefully adapting the existing tools (the OCamllex lexer and Menhir parser generators) to better support incrementality, incompleteness and error handling. These extensions are elegant and general, as demonstrated by the interesting, unplanned uses that the OCaml community found for them. They could be adapted to other frontends -- in any language. Besides incrementality, we discuss the way Merlin communicates with editors, describe the design decisions that went into some demanding features and report on some of the non-apparent difficulties in building good editor support, emerging from expressive programming languages or frustrating tooling ecosystems. We expect this experience report to be of interest to authors of interactive language tooling for any programming language; many design choices may be reused, and some hard-won lessons can serve as warnings.

P31. Gait disturbance in patients with orthostatic tremor

Introduction Orthostatic tremor (OT) is a rare disorder of unclear etiology characterized by a 13–18 Hz tremor of the legs while standing with resolving symptoms during sitting or walking. OT is associated with other movement disorders such as parkinsonism, essential tremor or cerebellar disorders. Although gait disturbances are frequently described in these diseases, there is no systemic analysis of the gait disorder linked to OT. Therefore, the aim of this study is to investigate the gait performance of patients with OT assessed by a standardized sensorimotor and cognitive walking paradigm. Methods Patients with a diagnosis of primary OT were screened and included in this study after informed consent. Gait performance was investigated during 8 different walking conditions using a pressure-sensitive sensor carpet (GAITRite®). Patients walked at preferred, slow and maximum walking speeds (PS, SS, MS), during head reclination and eyes closed conditions (HR, EC) as well as calculatory, semantic and motoric dual task conditions (DTC, DTS, DTM). The gait performance of patients was compared to age-matched healthy subjects. Gait parameters were assessed by a multivariate analysis of variance. Results Eighteen patients with a diagnosis of primary OT with a mean age of 70.4 ± 5.9 years were included in the study. In all walking conditions gait velocity (p Discussion Although OT symptoms diminish during walking, we identified constant impairments of locomotion control. The gait disturbance was characterized by an increased level of a cautious gait (slow, small-stepped, increased double support phases and BOS). Moreover, we identified disturbance of gait stability (increased CV) and interlimb coordination (left-right asymmetry). The specific alterations were found in conditions with increased sensory feedback control as well as attentional cognitive gait control. This implies an impaired integration of sensory feedback, possibly due to a dysfunction of midline cerebellar structures, as cerebellar dysfunction in OT was frequently described.

Parity, Relevance, and Gentle Explosiveness in the Context of Sylvan's Mate Function

The Routley star, an involutive function between possible worlds or set-ups against which negation is evaluated, is a hallmark feature of Richard Sylvan and Val Plumwood's set-up semantics for the logic of first-degree entailment. Less frequently acknowledged is the weaker mate function described by Sylvan and his collaborators, which results from stripping the requirement of involutivity from the Routley star. Between the mate function and the Routley star, however, lies an broad field of intermediate semantical conditions characterizing an infinite number of consequence relations closely related to first-degree entailment. In this paper, we consider the semantics and proof theory for deductive systems corresponding to set-up models in which the mate function is cyclical. We describe modifications to Anderson and Belnap's consecution calculus LE_fde2 that correspond to these constraints, for which we prove soundness and completeness with respect to the set-up semantics. Finally, we show that a number of familiar metalogical properties are coordinated with the parity of a mate function's period, including refined versions of the variable-sharing property and the property of gentle explosiveness.

Associations between semantic priming and problem behavior in boy with attention deficit hyperactivity disorder

Objective To investigate the semantic priming of boy with attention deficit hyperactivity disorder(ADHD) and explore whether the semantic priming deficits was associated with behavioral problems by event-related potential(ERP). Methods Thirty boy with and without ADHD aged from 7 to 13 years were asked to finish the semantic Semantic judgment task.The study took advantage of t-test(independent-samples) to compare the amplitude and latency of the N400 in both groups, as well as behavioral data.Behavioral problems were assessed by the Achenbach child behavior checklist(CBCL), and Pearson correlation analysis were used to explore the relationship between behavioral problems and semantic priming. Results Under the condition of semantic correlation, the hyperactive factor of CBCL in ADHA group was positively correlated with ERP N400 amplitude (r=0.44, P<0.05) and negatively correlated with reaction accuracy (r=-0.48, P<0.05). Under the semantic irrelevant condition, the latency of ERP N400 in ADHA group was positively correlated with hyperactivity factor (r=0.53, P<0.05)and aggression factor of CBCL(r=0.62, P<0.05). The N400 amplitude of the ADHD group was significant higher than that in the control group under semantic related conditions((-11.36±4.77)μV vs (-7.66±5.24)μV, P=0.006), and the latency of the N400 in ADHD was more delay((369.6±44.09)ms vs (341.27±24.54)ms, P=0.004), and the reaction times(RT) was much longer((936.18±135.03)ms vs (857.78±103.45)ms, P=0.014). The latency of the N400 in ADHD was more delay than that in the control group under semantic irrelevant conditions((383.93±29.66)ms vs (362.33±29.66)ms, P=0.012), and accuracies of ADHD group was lower than that of control group(0.43±0.39 vs 0.81±0.23, P<0.01). Conclusion The present result indicates that children with ADHD exhibit a deficit in the semantic priming mechanism, and the deficit is positively correlated with hyperactivity and impulsiveness. Key words: Semantic priming; Attention deficit hyperactivity disorder; Behavior problem; ERP; N400

Null objects in the spontaneous speech of monolingual and bilingual speakers of European Portuguese

AbstractThis paper investigates object omissions in the spontaneous production of European Portuguese by second-generation Portuguese-German bilingual speakers and compares them to first-generation migrants, and two age-matched groups of monolingual speakers. The results show that bilingual speakers as well as the younger generation of monolinguals show a higher number of null objects in their speech than the two older generations. This may reflect an inter-generational development that favours null objects, which is independent of language contact. The analysis of the syntactic and semantic conditions determining the occurrence of null objects in the speech of the different groups reveals that the semantic properties of the null objects realized by the bilinguals, particularly the higher rates of animate and non-propositional null objects, show that they extend the semantic-pragmatic conditions of null object realization along a referential hierarchy. The bilingual speakers may reflect a language-internal pathway that appears to resemble a diachronic change observed in BP.

When regularization gets it wrong: children over-simplify language input only in production.

Children tend to regularize their productions when exposed to artificial languages, an advantageous response to unpredictable variation. But generalizations in natural languages are typically conditioned by factors that children ultimately learn. In two experiments, adult and six-year-old learners witnessed two novel classifiers, probabilistically conditioned by semantics. Whereas adults displayed high accuracy in their productions - applying the semantic criteria to familiar and novel items - children were oblivious to the semantic conditioning. Instead, children regularized their productions, over-relying on only one classifier. However, in a two-alternative forced-choice task, children's performance revealed greater respect for the system's complexity: they selected both classifiers equally, without bias toward one or the other, and displayed better accuracy on familiar items. Given that natural languages are conditioned by multiple factors that children successfully learn, we suggest that their tendency to simplify in production stems from retrieval difficulty when a complex system has not yet been fully learned.

ДОСЛІДЖЕННЯ ПОКАЗНИКІВ ПРОФЕСІЙНОЇ САМОІДЕНТИФІКАЦІЇ МАЙБУТНІХ АГРАРІЇВ В УМОВАХ ПРОФЕСІЙНОГО НАВЧАННЯ

In the article provided the research results of component indicators that define the professional identity of agrarian students while the period of training and education. Empirical data defined the determinant biographical indicators that influence the formation of professional self-identification, namely, positive experience of the student’s work in the agricultural sector and the positive emotional and appraisal of the individual’s view of the future profession formed on the basis of monitoring the professional activities of specialists in the agricultural sector. It is revealed that professional self-identification is a product of long-term personal and professional development, which appears in the process of professional activity and obtaining professional experience. There are also defined the determining curriculum parameters of professional identity and the scheme of professional identity components of agrarian students according to the training course. Presented the basic mechanisms of professional identity of the individual. Examined that the problem underlying the process of professional self-determination, which implies a deliberate act of career choices based on activation of the internal potential of the individual. Discovered professional identity as a semantic condition of professionalism formation that reflects the level of mastery by the human of the psychological structure of professional activity and providing of natural quality of self-realization. The notion was defined by serving an indicator of the internal maturity of the individual as a manifestation of professional identity, providing some stabilizing functions of socialization and integration of subject-object relations in professional activities.

Inference of static semantics for incomplete C programs

Incomplete source code naturally emerges in software development: during the design phase, while evolving, testing and analyzing programs. Therefore, the ability to understand partial programs is a valuable asset. However, this problem is still unsolved in the C programming language. Difficulties stem from the fact that parsing C requires, not only syntax, but also semantic information. Furthermore, inferring types so that they respect C's type system is a challenging task. In this paper we present a technique that lets us solve these problems. We provide a unification-based type inference capable of dealing with C intricacies. The ideas we present let us reconstruct partial C programs into complete well-typed ones. Such program reconstruction has several applications: enabling static analysis tools in scenarios where software components may be absent; improving static analysis tools that do not rely on build-specifications; allowing stub-generation and testing tools to work on snippets; and assisting programmers on the extraction of reusable data-structures out of the program parts that use them. Our evaluation is performed on source code from a variety of C libraries such as GNU's Coreutils, GNULib, GNOME's GLib, and GDSL; on implementations from Sedgewick's books; and on snippets from popular open-source projects like CPython, FreeBSD, and Git.

The neural realm of taxonomic and thematic relation: an fMRI study

ABSTRACTTaxonomic and thematic relations are part of an integrated memory system grounded in the sensory, perceptual and motor systems and distributed across important brain regions. Although essential for human communication and cognition, their neural basis is still a point of controversy. This study used neuroimaging to demonstrate the involvement of the frontal, parietal, occipital and temporal regions in comparison to the control (pseudo-word condition). Subjects underwent functional magnetic resonance imaging (fMRI) during an auditory semantic priming task involving decision-making about similarities of the presented word pairs based on taxonomic and thematic relations. The precise common region was identified as the ventral occipito-temporal cortex. Direct comparison across semantic conditions indicated that the inferior frontal, supramarginal gyrus, medial and anterior temporal poles were involved as key regions for taxonomic relations. Additional regions for thematic relations were not identified, thus implying the possibility of highly variable nature of taxonomic and thematic relation.

Continued search for better prediction of aided speech understanding in multi-talker environments

To better understand issues of hearing-aid benefit during natural listening, this study examined the added demand placed by the goal of understanding speech over the more typically studied goal of simply recognizing speech sounds. The study compared hearing-aid benefit in two conditions, and examined factors that might account for the observed benefits. In the phonetic condition, listeners needed only identify the correct sound to make a correct response. In the semantic condition, listeners had to understand what they had heard to respond correctly, because the answer did not include any keywords from the spoken speech. Hearing aids provided significant benefit for listeners in the phonetic condition. In the semantic condition on the other hand, there were large inter-individual differences, with many listeners not experiencing any benefit of aiding. Neither a set of cognitive and linguistic tests, nor age, could explain this variability. Furthermore, analysis of psychometric functions showed that enhancement of the target speech fidelity through improvement of signal-to-noise ratio had a larger impact on listeners' performance in the phonetic condition than in the semantic condition. These results demonstrate the importance of incorporating naturalistic elements in the simulation of multi-talker listening for assessing the benefits of intervention in communication success.